Many products have been utilized as electrophotographic photoreceptors in electrophotography. Electrophotographic photoreceptors are used in the processes of charging, exposure and development. Examples of electrophotographic photoreceptors include: (1) light conductive organic materials directly applied onto a suitable conductive substrate by coating or by deposition; (2) inorganic photoconductive materials such as ZnO and CdS dispersed in binder resin; (3) amorphous Se, Se-Te alloy or Se-As alloy emplaced by deposition; and (4) two or more laminated layers of the above-mentioned photoconductive layers.
These conventional electrophotographic photoreceptors, when used repeatedly, tend to suffer surface damage during electrical and mechanical electrophotographic processes such as charging, exposure, development and copy cleaning There have been various prior proposals for preventing damage to the surface of the photosensitive layer by furnishing a protective surface layer on the photosensitive layer. (For example, JP-A-61-205950 (the term "JP-A" as used herein means an "unexamined and published Japanese Patent application").)
The characteristics required for protecting surface layers of electrophotographic photoreceptors are that they have the durability to withstand the several treatments involved in electrophotographic processes as described above. Because the surface layers can become contaminated by residual toner particles, paper dust from the copy paper, other charged materials, and the like, it is particularly necessary that they can be thoroughly cleaned without causing damage to the surface. The conventional art has not provided a satisfactory solution to these problems.